A communication system can be seen as a facility that enables communication sessions between two or more entities such as mobile communication devices and/or other associated with the communication system. A communication system and a stations compatible communication device typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. For example, the standard or specification may define if a communication device is provided with a circuit switched carrier service or a packet switched carrier service or both. Communication protocols and/or parameters which shall be used for the connection are also typically defined. For example, the manner how the communication device can access the communication system and how communication shall be implemented between communicating devices, the elements of the communication network and/or other communication devices is typically based on predefined communication protocols.
In a wireless communication system at least a part of the communication between at least two stations occurs over a wireless link. Examples of wireless systems include public land mobile networks (PLMN), satellite based communication systems and different wireless local networks, for example wireless local area networks (WLAN). The wireless systems can be divided into cells, and are therefore often referred to as cellular systems.
A user can access the communication system by means of an appropriate communication device. A communication device of a user is often referred to as user equipment (UE). A communication device is provided with an appropriate signal receiving and transmitting arrangement for enabling communications with other parties. Typically a communication device is used for enabling the users thereof to receive and transmit communications such as speech and data. In wireless systems a communication devices provides a transceiver station that can communicate with e.g. a base station of an access network servicing at least one cell and/or another communications device. Depending on the context, a communication device or user equipment may also be considered as being a part of a communication system. In certain applications, for example in ad-hoc networks, the communication system can be based on use of a plurality of user equipment capable of communicating with each other.
The communication may comprise, for example, communication of data for carrying communications such as voice, electronic mail (email), text message, multimedia and so on. Users may thus be offered and provided numerous services via their communication devices. Non-limiting examples of these services include two-way or multi-way calls, data communication or multimedia services or simply an access to a data communications network system, such as the Internet. The user may also be provided broadcast or multicast content. Non-limiting examples of the content include downloads, television and radio programs, videos, advertisements, various alerts and other information.
3rd Generation Partnership Project (3GPP) is standardizing an architecture that is known as the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology. The aim is to achieve, inter alia, reduced latency, higher user data rates, improved system capacity and coverage, and reduced cost for the operator. A further development of the LTE is referred to herein as LTE-Advanced. The LTE-Advanced aims to provide further enhanced services by means of even higher data rates and lower latency with reduced cost. The various development stages of the 3GPP LTE specifications are referred to as releases.
Since the new spectrum bands for international mobile telecommunications (IMT) contain higher frequency bands and LTE-Advanced is aiming at a higher data rate, coverage of one Node B (base station) can be limited due to the high propagation loss and limited energy per bit. Relaying has been proposed as a possibility to enlarge the coverage. Apart from this goal of coverage extension, introducing relay concepts may also help in the provision of high-bit-rate coverage in a high shadowing environment, reducing average radio-transmission power at the User Equipment (UE). This may lead to long battery life, enhanced cell capacity and effective throughput, e.g., increasing cell-edge capacity, balancing cell load, enhancing overall performance, and reducing deployment costs of radio access networks (RAN). The relaying would be provided by entities referred to as Relay stations (RSs) or Relay Nodes (RNs). The relay nodes can be fixed or mobile, for example mounted to a high-speed train. In some systems the relay stations may be opportunistically available user equipment/mobile terminals that are not owned by the network itself.